U.N. envoy Kofi Annan called on the Assad regime to halt the violence, saying there was still time to salvage a truce. Annan insisted his peace initiative remains "very much alive" - in part because there is no viable alternative.

The Syrian government says it is pulling back some troops ahead of Thursday's complete cease fire, including the rebellious central province of Homs. But France called the claims a "flagrant and unacceptable lie," and activists said there was no sign of a withdrawal.

The halt in fighting would pave the way for talks between both sides over the country's future and an observer mission.